Fluorescent Minerals

by

Jerry Harvey

Calcite under shortwave UV (blue)
Calcite under longwave UV (pink)
Images taken from
http://users.rcn.com/kenx/

Have you ever wondered where the bright colors come from when you view a certain mineral under a black light? Minerals can emit light through several different means. The minerals can emit light from daylight and from light bulbs. The chemicals in the minerals react with the use of an ultra violet (UV) light source, and start to glow. The glow is a phenomenon known as fluorescence. (1)

Franklinite Under UV Light
Image taken from
http://www. mineralarts.com/micromin/flurescent.html

So how do these special minerals emit fluorescent light? When the UV light hits the mineral electrons become "excited" and jump to a higher energy state. The electron then falls back and releases its energy in the form of visible light. The light that is emitted is very colorful and can be very different from the color of the mineral. (3)

Fluorescence with shortwave ultraviolet light at the left.
Same minerals shown to the right under white light.

Images taken from
http://home.pacifier.com/~leopard/

There are two different kinds of ultraviolet light, longwave and shortwave. The black light that almost everyone is familiar with is longwave UV. Shortwave UV light has a shorter wavelength than longwave UV light, 254 nanometers for shortwave and 366 nanometers for longwave. Some minerals respond to both sources of UV light with the same or similiar colors, while some may show different colors under each source like the calcite at the top of the page. (1)

So what causes minerals to have fluorescence? The minerals have special atoms that undergo fluorescence which are known as activators. (2) These activators are present in the minerals as part of the molecular structure or mostly as impurities in the mineral. Because the activators are usually impurities, the same species of mineral may show fluorescence in one location and may not in another. It may also have had different activators when it formed, and have different colors. (1)

Calcite with different colors and from different locations.
http://home. pacifier.com/~leopard/fluorex.htm

Along with fluorescence, minerals can show phosphorescence, thermoluminescence, and triboluminescence. Minerals that remain glowing for a few seconds after the UV light source is removed are said to be phosphoresent. Thermoluminescence refers to the glowing from a mineral that has been heated. Some minerals can glow after they have been struck or crushed and this is called triboluminescence. (1)

References Cited

1.Amethyst Galleries, Inc. (1995-2002). The Mineral Gallery. World Wide Web URL: http://mineral.galleries.com/minerals/property/fluoresc.htm. Retrieved on 17 November, 2002.

2. Rodriquez, M. 1992-2000. Glow Rocks An Overview of Fluorescent Minerals. World Wide Web URL: http://www.glowrocks.com/info/describe.html. Retrieved on 17 November, 2002.

3. DeVroeg, E. (2000). The Phenomenon of Fluorescence. Fluorescent Mineral Gallery. World Wide Web URL: http://home. pacifier.com/~leopard/fluorex.htm. Retrieved on 17 November, 2002.

4. Robbins, Manuel (1994). Fluorescence: Gems and Minerals Under Ultraviolet Light. Phoenix, Ariz.: Geoscience Press.

5.Moore, D. (1999). Fluorescent Minerals. Minerals Under the Microscope. World Wide Web URL: http://www.mineralarts.com/micromin/fluorescent.html. Retrieved on 17 November, 2002.

6. Colosky, K. (1995). Ken's Fluorescent Minerals. World Wide Web URL: http://users.rcn.com/kenx/. Retrieved on 19 November, 2002.

About This Page

This page was created by a college student for my mineralogy course, http://www.emporia.edu/earthsci/amber/go336/, from Emporia State University, http://www.emporia.edu. Feel free to e-mail me at jockster00@hotmail.com. This page was created on November 17, 2002.

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